thanks again....your one reply now generate a thousands other threads of questions....:-)....thanks for the trouble taken...programming is hardwork!!! On Thu, May 29, 2008 at 4:25 PM, Vegard Nossum <vegard.nossum@xxxxxxxxx> wrote: > On 5/29/08, Peter Teoh <htmldeveloper@xxxxxxxxx> wrote: >> Hi Vegard, I have some questions for you. >> > > [...] > >> Second, your present tried to retain the CR3 value, but change the >> contents of the page table instead....but has problem with >> multiprocessor. >> >> How about the other way round - change the contents of per-CPU CR3, >> which will point to a different pagetable - (subtable). Not sure if >> this is the "per-cpu" pagetable that Ingo is suggesting to you. But >> I am suggesting a very small subtable - only those entries needed are >> constructed. After use it will be switch back to the original CR3. >> Possible? > > Hi, > > Sorry for the short reply but I am short on time :) > > So this is actually a very good idea. I previously disregarded it as > impossible because you can have for example a CMPS instruction that > compares (in fact) TWO memory locations). But it shouldn't be worse > than simply making two entries in that new page table :-) > > For this, we would only need as many pages as we have levels in the > page table, e.g. two or three extra pages per CPU. And we only have to > copy at most two words per level, i.e. at most 6 reads/writes. This > will certainly be a killer if it works. > > (The most overhead I'm guessing will come from reloading the CR3 twice > on each #PF. But then again, it might not be so much compared to what > we already do. I honestly don't know! It's much, much better than > halting all the other CPUs, though!) > > Thanks a lot for this suggestion! I will try to implement the idea and > see if I can find any fatal consequences. > > Vegard > > -- > "The animistic metaphor of the bug that maliciously sneaked in while > the programmer was not looking is intellectually dishonest as it > disguises that the error is the programmer's own creation." > -- E. W. Dijkstra, EWD1036 > -- Regards, Peter Teoh -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
